1. Field of the Invention
The present invention relates to a thermally assisted magnetic recording head including an optical near-field generator and a magnetic recording device using the thermally assisted magnetic recording head.
2. Background Art
A thermally assisted magnetic recording system has been recently proposed as a recording system that realizes a recording density of 1 Tb/in2 or higher (H. Saga, H. Nemoto, H. Sukeda, and M. Takahashi, Jpn. J. Appl. Phys. 38, Part 1, 1839 (1999)). With a conventional magnetic recording device, loss of recorded information due to thermal fluctuation problematically occurs at a recording density of 1 Tb/in2 or greater. While a coercive force of the magnetic recording device must be increased in order to prevent such information loss, since there is a limit to the magnitude of a magnetic field that can be generated from a recording head, excessively increasing the coercive force makes it impossible to form recorded bits on a medium. In order to solve this problem, the thermally assisted magnetic recording system heats a medium at the instant of recording to reduce coercive force. Consequently, recording can be performed on a high-coercive force medium and a recording density of 1 Tb/in2 or greater can be realized.
In the thermally assisted magnetic recording device, a spot diameter of irradiated light must approximately match the size of a recorded bit (several 10 nm). This is because information on an adjacent track ends up being erased if a light spot diameter is greater than the size of a recorded bit. An optical near-field is used to heat such a minute area. An optical near-field is a localized electromagnetic field (a light whose wave number has an imaginary component) existing in the vicinity of a minute object that is equal to or smaller than light wavelength and is generated using a minute opening or a metallic scatterer whose diameter is equal to or smaller than light wavelength. For example, Japanese Patent Publication (Kokai) No. 2001-255254A proposes an optical near-field generating element using a triangular metallic scatterer as a high-efficiency optical near-field generating element. When light is incident to the metallic scatterer, a plasmon resonance is excited within the metallic scatterer and an intense optical near-field is generated at a vertex of the triangle. The use of the optical near-field generating element enables light to be collected in a highly efficient manner at an area of several 10 nm or smaller. In addition, Japanese Patent Publication (Kokai) No. 2004-151046A proposes a structure in which, on a surface of the metallic scatterer on a side of a slider air-bearing surface, a depression is carved on the surface in a part other than a vertex where an optical near-field is generated. The structure enables reduction of a width of an intensity distribution of the optical near-field generated at the vertex and, at the same time, enables suppression of the generation of a weak optical near-field (background light) generated on a side opposite to the vertex.